Comparative evaluation of three commercial Toxoplasma-specific IgG antibody avidity tests and significance in different clinical settings
ABSTRACT Determination of the avidity of specific IgG antibodies has become a generally accepted diagnostic aid for dating Toxoplasma infection. In this study, the Labsystems, VIDAS and EUROIMMUN Toxoplasma IgG avidity assays were compared on a series of 133 Toxoplasma IgG- and IgM-positive sera from symptomatic patients (n=28), from pregnant (n=43) and non-pregnant (n=26) women, and on 18 IgG-positive and IgM-negative sera from chronically infected patients. The results showed excellent concordance between the Labsystems and VIDAS tests in both the IgM-positive (r=0.82, kappa=0.771) and IgM-negative (kappa=0.609) sera, whilst the agreement of the EUROIMMUN assay with both the Labsystems and VIDAS tests in the IgM-positive sera was moderate (kappa=0.575 and kappa=0.525, respectively) and in the IgM-negative sera was poor (kappa=0.000). Analysis of the kinetics of the maturation of avidity in 13 patients in whom follow-up sera were available showed that, despite a general trend of maturation, in two patients the avidity did not become high during 6 and 11 months of follow-up. In view of the clinical setting, in the symptomatic patients, despite one case of complete discrepancy and five cases of partial discrepancy, the Labsystems and VIDAS tests were in almost perfect agreement (kappa=0.812), whilst the agreement in pregnant and non-pregnant women was substantial (kappa=0.754 and kappa=0.708, respectively). In conclusion, the Labsystems and VIDAS tests are equally reliable for the measurement of Toxoplasma IgG avidity; the choice of test should depend on the laboratory set-up. The EUROIMMUN test may be an acceptable alternative in resource-limited settings, but should be used prudently.
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ABSTRACT: Seasonal variations in the occurrence of toxoplasmosis have been studied only sporadically. We thus examined the seasonal distribution of acute toxoplasmosis in Serbia during a 4-year period (2004-2008). A total of 391 consecutive symptomatic (recent lymphadenopathy) and 715 asymptomatic (women tested for obstetric reasons) patients were tested for Toxoplasma immunoglobulin G (IgG) (including IgG avidity) and IgM antibodies. The distribution of patients with acute infection, and of all patients from both groups, was analyzed for seasonality. In addition, factors (including undercooked meat consumption, contact with cats and with soil) possibly contributing to seasonality were analyzed in patients with acute infection (cases) matched by age, sex, and time (month and year) of infection (symptomatic) or presentation (asymptomatic) with seronegative patients (controls). Acute toxoplasmosis was serologically (IgG avidity low, IgM positive) diagnosed in 39 (10.0%) symptomatic and 38 (5.3%) asymptomatic patients. In both groups, monthly distribution of acute infections showed significant (p < 0.0001) seasonality, which was related to the four seasons of the year (p < 0.0001). Importantly, the observed seasonality was not related to the distribution of all examined patients in either group (p < 0.001). In the symptomatic patients, acute infections occurred more often between October and March (p = 0.0486). Although more asymptomatic acute infections were diagnosed between February and July (p = 0.0037), low IgG avidity suggests that infection had occurred within the previous trimester (between November and April). Undercooked meat consumption was shown as a risk factor for symptomatic infection in the October-March period (odds ratio 7.67, 95% confidence interval 1.61-36.45). Seasonality patterns should be taken into account in the health education guidelines for the prevention of toxoplasmosis in pregnant women.Vector borne and zoonotic diseases (Larchmont, N.Y.) 12/2009; 10(5):465-9. DOI:10.1089/vbz.2009.0153 · 2.30 Impact Factor
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ABSTRACT: Toxoplasma gondii is an important human pathogen with a worldwide distribution. It is primarily of medical importance for pregnant women and immunocompromised patients. Primary infection of the former is often associated with fetal infection, which can lead to abortion or severe neonatal malformation. Immunocompromised patients are at risk of contracting the severe form of the disease that may be fatal. Thus, detection of T. gondii infection with high sensitivity and specificity is crucial in the management of the disease. Toxoplasmosis is generally diagnosed by demonstrating specific immunoglobulin M (IgM) and IgG antibodies to toxoplasma antigens in the patient's serum sample. Most of the commercially available tests use T. gondii native antigens and display wide variations in test accuracy. Recombinant antigens have great potential as diagnostic reagents for use in assays to detect toxoplasmosis. Thus in this review, we address recent advances in the use of Toxoplasma recombinant proteins for serodiagnosis of toxoplasmosis.Apmis 08/2010; 118(8):529-42. DOI:10.1111/j.1600-0463.2010.02629.x · 2.04 Impact Factor